Two-thirds of the >38 million people with HIV/AIDS reside in Sub-Saharan Africa. Access to antiretroviral therapy (ART) in less wealthy nations is expanding quickly, creating an urgent need to understand those factors influencing adherence, a key determinant of ongoing efficacy of ART, so that the creation and spread of medication-resistant virus is limited. The proposed research team has identified suboptimal adherence among 29% of clinic attendees taking ART for >6 months in Moshi Tanzania, while documenting lack of virologic suppression in 32% and antiretroviral drug resistance in 10%. We propose to follow 750 newly diagnosed HIV+ persons, 500 previously diagnosed HIV+ persons and 750 HIV-negative persons in over 3 years in this region. The newly diagnosed HIV+ and HIV- cohorts will be obtained through consecutive sampling in a Voluntary Counseling and Testing (VCT) site and the on-going HIV+ cohort will be similarly drawn from the Infectious Disease Clinic (IDC) in the tertiary care medical center 5 miles away. This research team has a track record of successful past and ongoing research at both the VCT and the IDC sites. Baseline data we will used to examine associations between psychosocial (including trauma, mental health symptomatology, coping strategies and life events), sociodemographic, and economic factors and health status, adherence to ART, and health promotion and high risk activities. Longitudinal analyses will examine causal relationships between changes in the independent and dependent variables. Results will lead to the creation of more effective prevention and care models for the area and other similar areas. Studying the population of ART naive patients in a resource poor setting provides a unique window of opportunity to gather data designed to increase our understanding of underlying variables associated with maladherence and risk behaviors. Psychosocial determinants are a unique strength of this proposal. The study will result in a minimum of 7 peer reviewed articles and dissemination of findings at annual national (US and Tanzanian) and international AIDS, Public Health and Mental Health conferences, including the annual Tanzania national AIDS conference. A policy related report will be disseminated to national and international leaders.